Dewaxing mineral oils



Jan. 5, 1937 R. E, MANLr-:Y

DEWAXING MINERAL OILS Original Filed Dec. 14, 1931 Patented Jan. 5 1937 PATENT OFFICE DEWAmG MINERAL OILS Robert E. Manley, Beacon, N. Y., assignor to The Texas Company, New York, N. Y., a corporation of Delaware Refiled for abandoned application Serial No.

581,057, December 14, 1931.

This application June 19, 1935, Serial No. 27,371

11 Claims.

This invention relates' to a process for the removal of wax from wax-bearing hydrocarbon oil, and more particularly to the removal of wax from petroleum oil for the production of low pour 5 test lubricating oil. y

'I'he present application is a substitute application for my previous application, Serial Number- 581,057, filed December 14. 1931, for Dewaxing mineral oils.

lo The invention contemplates a process of dewaxing hydrocarbon oils comprising adding to the oil a solvent liquid to form a mixture therewith from which, upon cooling, the wax constituents are precipitated, then admixing with the mixl5 ture of oil and solvent a liquid refrigerant material which is adapted to .be refrigeratively evaporated therefrom to thereby chill the mixture to a temperature at which the wax constituents are precipitated as solid hydrocarbons. The solid 20 hydrocarbons are separated from the solution while maintaining the solution in a cold condition, and the solvent and retained refrigerant liquid is evaporated from the resulting filtrate to produce an oil of `desired low pour test.

25 The invention comprises mixing with the waxbearing oil a solvent liquid, such as petroleum naphtha, orI a,l mixture of acetone and benzol. A suitable solvent liquid may alsoiembrace such solvents as alcohols, ketones, aldehydes, hydro- 80 carbons, including benzenoid hydrocarbons, and organic acids, homologs and derivatives of these various solvent materials or mixtures thereof having suitable selective solvent properties between liquid and solid hydrocarbons. Advantageously 35 a suitable selective solvent is a liquid or mixture of liquids which has substantially completev solvent action on wax-bearing mineral oil at temperatures of around 100 F. and at temperatures of 5 F. and below has substantially complete sol- 40 vent action on the liquid hydrocarbons therein but substantially no solvent action on the solid hydrocarbons therein and of such a nature that upon cooling a solution of such wax-bearing mineral oil in the solvent to F. and removing the 45 solid hydrocarbons so precipitated and the solvent the resulting oil has a pour test of substantially 0 F.

To the solvent solution of wax-bearing oil, the refrigerant liquid is added, which may comprise 50 a volatile liquid which is gaseous at normal atmospheric temperature and pressure, and which may advantageously include such refrigerant liquids as carbon dioxide, anhydrous ammonia, sulphur dioxide, or low boiling hydrocarbons such 55 as propaneybutane, homologs thereof, as well as their derivatives such as halogenated hydrocarbons which are suitable as refrigerants.

The refrigerant material is advantageously of the type which is miscible with the oil and also possesses some solvent action upon the liquid hydrocarbons so that it not only combines the function of a refrigerating medium but also that of a selective solvent. Liquid carbon dioxide, anhydrous ammonia, ethyl chloride, and sulphur dioxide, for example, are all miscible with mineral oils in varying extent and, in addition, possess desirable solvent properties for mineral oils, or the various constituents thereof, thus rendering their use of particular advantage in connection with the dewaxing of wax-bearing oilv according l5 to the process of my invention for the production of lubricating oils having a low pour test as well as other desirable characteristics. These refrigerant materials which, in themselves, possess s01- vent properties for the oil and are miscible therewith may, in some instances be used in the dual capacity of a wax-precipitating medium and refrigerating medium without the addition to the wax-bearing oil of the previously mentioned selective solvent, but non-refrigerant, liquid.

The refrigerant liquid is admixed with the solution while maintained under pressure sufcient to keep it in a liquid condition. The resulting mixture may be subjected to precooling by passing it in indirect heat exchange. relationship with a stream of dewaxed oil having undergone previous treatment. Following this, the solution is conducted into a zone of relatively lower pressure wherein all or a portion of the refrigerant liquid is evaporated from the solution with refrigerative effect to thereby chill it to a temperature of around 0 F. or lower so as to precipitate its wax constituents.

An important advantage of my invention consists in admixing with the wax-bearing oil a solvent or mixture of solvent liquids which not only possess selective solvent properties between the liquid and solid hydrocarbon constituents, but also which serves as a refrigerating medium upon evaporation of a portion of the material directly from the solution. In this way, chilling or cooling of the solution to low temperatures is much more economically and effectively accomplished than by the methods heretofore employed wherein cooling of the solution has been effected by indirect heat interchange with a circulating brine. These latter methods have required the employment of separate refrigerating plants, which is unnecessary when operating in accordance with the process of my invention.

A still further advantage accrues as a result of mixing the liquid refrigerant material with the wax-bearing solution due to the resulting decrease in viscosity of the ultimate mixture. In general, refrigerant materials of the type disclosed above, which are gaseous at normal atmospheric temperatures and pressures, have a relatively low absolute viscosity. Consequently, the resulting admixture with the wax-bearing solution is also of relatively lower viscosity than would otherwise be the case. It has been found that the crystallization and precipitation of wax in a readily iilterable form from wax-bearing oils is better facilitated from a relatively nonviscous mixture or solution. It has further been found that precipitating, as well as subsequent complete removal of the precipitated wax by filtration, is hindered, to an appreciable extent, where the liquid medium from which the wax is being precipitated and filtered is of a viscous nature.

In carrying out the process of my invention, a solvent liquid, which may be eithera mixture of acetone and benzol, or a low-boiling hydrocarbon fraction by itself, is mixed with the waxbearing mineral oil in suitable proportion. The refrigerant liquid, such as carbon dioxide or ammonia, is introduced to the body of oil and solvent contained in a closed tank wherein the liquid may be confined under sufficient pressure to maintain the refrigerant material in a liquid condition. Intimate mixing of the refrigerant with the wax-bearing solution can be effected by recirculation of a portion of the contents of the tank or mechanically by means of suitable stirring mechanism.

The mixture of oil, solvent and refrigerant is then subjected to cooling and chilling to a temperature at which the wax constituents separate from the oil, which may be a temperature ranging from around 0 F. to 30 F. or lower, depending upon the desired pour test of the final product. This chilling is brought about by introducing the mixture'to a zone of relatively lower pressure, wherein a portion of the refrigerant is caused to evaporate from the mixture with refrigerative effect, thereby cooling the remaining body of liquid. Advantageously additional quantities of the refrigerant liquid may be introduced directly into the body of solution while in this chilling zone so as to supply the necessary amount of liquid for evaporation and also maintain the desired quantity of such liquid present as a solvent or as a diluent in admixture with the oil during and subsequent to the chilling.

To further illustrate the invention, reference will now be made to the accompanying drawing which illustrates one method of carrying out the process.

The wax-bearing oil to be treated is conducted from a tank I to a mixer 2 wherein it is mixed with solvent drawn from a tank 3 and which, for example, may comprise a mixture of acetone and benzol or a solvent liquid having antisolvent properties for wax.

The mixture of oil and solvent is then delivered to a vessel 4 wherein it is further mixed with the refrigerant and diluent material as, for example, a light petroleum hydrocarbon such as propane, drawn from a tank 5. The vessel 4 is also provided with agitating or stirring means 6 to effect complete mixing between the solution and the propane. It is also maintained under suflicient pressure to maintain the propane in liquid form.

The resulting mixture is then delivered from the vessel 4 by pump 1 through pipe 8 to a chiller 9. The chiller 9 is of the indirect type wherein the mixture of wax-bearing oil, solvent, and propane is brought into indirect heat relationship with a cold body of dewaxed mixture from which propane is being refrigeratively vaporized, as will be described in more detail. I

The wax-bearing mixture, chilled to a temperature of 0? to 30 F., is Withdrawn from the chiller through a pipe I0 and delivered to filter II. If desired, a solid, inert, comminuted filter-aid material may be added to the cold mixture prior to introduction to the lter. In such case, the lter-aid material, preferably in the form of a slurry, is conducted from a tank I2 to a mixer I3 wherein it is intimately mixed with the cold wax-bearing mixture being delivered to the filter. Where it is not desired to employ filter-aid material, the cold wax-bearing mixture may be by-passed around the mixer through a pipe I4 directly to the filter II.

The wax filter cake formed in the filter is removed therefrom and delivered to a storage tank I5 while the resulting dewaxed mixture is conducted through a pipe I6 to the previously mentioned chiller 9.

This dewaxed mixture, comprising dewaxed oil, wax anti-solvent, and propane, is introduced to the chiller where it forms a cold body surrounding the coil I1 through which the fresh wax-bearing mixture is flowing. 'I'he interior of the chiller 9 is maintained under suciently low pressure so that evaporation of the` propane from the dewaxed mixture is brought about with refrigerative effect.

'I'he vaporized propane is drawn off from' the chiller 9 by a compressor I8. The compressed -propane is then conducted through a cooler I9 and returned in a liquefied state to the tank 5 previously mentioned.

The cold unvaporized liquid remaining in the chiller 9 is withdrawn through pipe 20 to a storage tank 2I. If desired, this cold mixture, all or in part, may be delivered by a pump 22 to a heat exchanger 23 wherein it is brought into indirect thermal contact with the fresh waxbearing mixture entering the chiller 9 to thereby pre-cool it.

An alternative method of accomplishing the chilling of the wax-bearing solution comprises passing the fresh solution in heat exchange relationship with a stream of previously dewaxed solution from which latter the refrigerant liquid is being evaporated with refrigerative eiect, thereby indirectly cooling the stream of fresh wax-bearing mixture or solution.

A combination of these two modes of operation may be utilized, if desired, and in any case it is advantageous to pre-cool the fresh mixture by passing it in indirect heat exchange relationship with an outgoing stream of cooled dewaxed oil from which the refrigerant material may or may not have been entirely evaporated so as to take advantage of as complete recovery of heat as is possible.

The chilled mixture containing precipitated wax suspended therein may, if desired, be commingled with a finely divided filter-aid material. The chilled mixture containing suspended solid material is then introduced to suitable filtering means, such as a pressure filter of the rotating leaf type, wherein it is subjected to filtration while maintained in a colcl4 condition in order to remove the suspended wax or admixture of suspended wax and filter-aid material, as the case may be.

The resulting filtrate comprising dewaxed oil in admixture with solvent and unevaporated refrigerant liquid may, as already indicated, be brought into indirect heat exchange relationship with fresh wax-bearing solution so as to pre-cool it and/or the refrigerant material evaporated therefrom while it is in indirect contact with the fresh wax-bearing solution.

Any solvent liquid or refrigerantk material remaining dissolved in, or in admixture with, the dewaxed oil after this evaporation step may be subsequently removed by subjecting the mixture to slight heating, and the evolved solvent and refrigerant material recovered for re-use in mixing with fresh wax-bearing oil which is to undergo treatment.

' In the foregoing example, the entire chilling of the oil and wax solution has been described as being effected by evaporating a refrigerant liquid material, gaseous at normal atmospheric temperature and pressure, either from the fresh solution or from the dewaxed solution while in indirect contact with the fresh solution. It is contemplated, however, that my invention is adapted to operate in conjunction with ordinary circulating brine refrigerating systems and the like. For example, a portion of the chilling of the solution, perhaps the initial or preliminary chilling thereof, may be effected by means of a circulating brine system While the nal chilling is accomplished by the method disclosed above, or vice-versa.

Obviouslymany modifications and variations of the invention, as hereinbefore set forth, may be made Without departing from the spirit and scope thereof, and therefore only such limitations should be imposed as are indicated in the appended claims.

I claim:

1. The method of dewaxing mineral lubricating oil which comprises mixing the wax-bearing oil with a selective solvent liquid having substantially complete solvent action upon the liquid constituents and substantially no solvent action on the solid wax constituents of the oil at temperatures of the order of 0 F. to -v-30" F. and comprising in part a normally gaseous diluent liquid, chilling the resulting mixture while owing in a stream in indirect thermal contact with a body containing a portion of said diluent undergoing refrigerative evaporation whereby said waxbearing stream is chilled to temperatures of 0 F. and below to solidify the wax, separating the solidified wax from the cold mixture, and refrigeratively vaporizing the diluent liquid contained in said dewaxed mixture while in indirect heat exchange relationship with said wax-bearing mixture to impart cooling thereto.

2. The method of dewaxing mineral lubricating oil which comprises mixing the wax-bearing oil with a selective solvent liquid having substantially complete solvent action upon the liquid constituents and substantially no solvent action on the solid wax constituents of the oil at temperatures of the order of 0 F. to 30 F. and comprising in part a volatile petroleum fraction of the character of propane and butane, chilling the resulting mixture while flowing in a stream in indirect thermal contact with a body containing a portion of said diluent undergoing refrigerative evaporation whereby said wax-bearing stream is chilled to temperatures of 0 F. and below to solidify the wax, separating the solidified wax from the cold mixture. and refrigeratively vaporizing the diluent liquid contained in said dewaxed mixture while in indirect heat exchange relationship with said wax-bearing mixture to impart cooling thereto.

3'. The method of dewaxing mineral lubricating oil which comprises mixing the wax-bearing oil with a selective solvent liquid having substantially complete solvent action upon the liquid constituents and substantially no solvent action on the solid wax constituents of the oil at temperatures of the order of 0 F. to 30 F. and comprising in part propane, chilling the resulting mixture while iiowing in a stream in indirect thermal contact with a body containing a portion of said diluent undergoing refrigerative evaporation whereby said wax-bearing stream is chilled to temperatures of 0 F. and below to solidify the wax, separating the solidified wax from the cold mixture, and refrigeratively vaporizing the diluent liquid contained in said dewaxed mixture `while in indirect heatexchange relationship with said wax-bearing mixture to impart cooling thereto.

4. Ihe method of dewaxing mineral lubricating oil which comprises mixing with the oil a. solvent liquid composed of an anti-solvent liquid for wax and a diluent liquid comprising a light petroleum fraction of the character of propane and butane in proportions such that at temperatures of below 0 F. the mixture has selective action as between wax and oil, chilling the resulting mixture while vowing in a stream in indirect thermal contact with a body containing a portion of said diluent undergoing refrigerative evaporation whereby said wax-bearing stream is chilled to temperatures of 0 F. and below to solidify the wax, separating the solidified wax from the cold mixture, and refrigeratively vaporizing the diluent liquid contained in said dewaxed mixture while in indirect heat exchange relationship with said wax-bearing mixture to impart cooling thereto.

5. The method of dewaxing mineral lubricating oil which comprises mixing with the oil a solvent liquid composed of an aliphatic ketone having wax anti-solvent properties characteristic of acetone and a diluent liquid comprising a light petroleum fraction of the character of propane and butane, chilling the resulting mixture while flowing in a stream in indirect thermal contact with a body containing a. portion of said diluent undergoing refrigerative evaporation whereby said wax-bearing stream is chilled to temperatures of 0 F. and below to solidify the wax, separating the solidified wax from the cold mixture, and refrigeratively vaporizing the diluent liquid contained in said dewaxed mixture while in indirect heat exchange relationship with said wax-bearing mixture to impart cooling thereto.

6. The method of dewaxing mineral lubricating oil which comprises mixing with the oil a solvent liquid composed of an anti-solvent liquid for wax and a diluent liquid comprising a light petroleum fraction of the character of propane and butane in proportions such that at temperatures of below 0 F. the mixture has selective action as between wax and oil, chilling the resulting mixture while flowing in a stream in indirect thermal contact with a body containing a portion of said diluent undergoing refrigerative evaporation whereby said wax-bearing stream is chilled to temperatures of F. and below to solidify the Wax, separating the solidified wax from the cold mixture by iiltration in the presence of a solid, inert, comminuted filter-aid material, and refrigeratively vaporizing the diluent liquid contained in said dewaxed mixture while in indirect heat exchange relationship with said wax-bearing mixture to impart cooling thereto.

l 7. The method of dewaxing mineral lubricating oil which comprises mixing the wax-bearing oil with a selective solvent liquid having substantially complete solvent action upon the liquid constituents and substantially no solvent action on the solid wax constituents of the oil at temperatures of the order of 0 F. to 30 F. and comprising in part sulphur dioxide, chilling the resulting mixture while flowing in a. stream in indirect thermal contact with a body containing a portion of said diluent undergoing refrigerative evaporation whereby said wax-bearing stream is chilled to temperatures of 0 F. and below to solidify the wax, separating the solidified wax from the cold mixture, and refrigeratively vaporizing the diluent liquid contained in said dewaxed mixture while in indirect heat exchange relationship with said wax-bearing mixture to impart cooling thereto.

8. The method of dewaxing mineral lubricating oil which comprises mixing the wax-bearing oil with a diluent composed of a volatile petroleum fraction of the character of propane and butane, chilling the dilute mixture while flowing in a coniined stream in indirect thermal contact with a cold body comprising a portion of said diluent undergoing refrigerative evaporation whereby said dilute stream is chilled to temperatures of the order of 0 F. and below to solidify 4the wax, separating the solidiiied wax from the diluent contained in said dewaxed mixture while in indirect heat exchange relationship with said conned stream of dilute mixture to impart cool-` ing thereto.

9'. The method of dewaxing mineral lubricating oil which comprises mixing the wax-bearing oil with a diluent comprising propane, chilling 1 the dilute mixture while owing in a conned stream in indirect thermal contact with a cold body comprising a portion of said diluent undergoing refrigerative evaporation whereby said dilute stream is chilled to temperatures of the order of 0 F. and below to solidify the wax, separating the solidified wax from the cold mixture, and refrigeratively vaporizing the diluent contained in said dewaxed mixture while in indirect heat exchange relationship with said confined stream of dilute mixture to impart cooling thereto.

10. The method of dewaxing mineral lubricating oil which comprises mixing the Wax-bearing oil with a diluent composed substantially of propane and butane in the proportion of about two parts of diluent to one part of oil, chilling the dilute mixture while iiowing in a confined stream in indirect thermal contact with a cold body comprising a portion of said diluent undergoing refrigerative evaporation whereby said dilute stream is chilled to temperatures of the order of 0 F. and below to solidify the wax, separating the solidied Wax from the cold mixture, and refrigeratively vaporizing the diluent contained in said dewaxed mixture while in indirect heat exchange relationship with said confined stream of dilute mixture to impart cooling thereto.

11. The process according to claim 8 in which the solidiiied wax is separated from the cold dilute mixture by iiltration in the presence of a solid, inert, iilter-aid material.

ROBERT E. MANLEY. 

